For instance, WO 2010/133491A1 teaches a header tank (collector box) of a heat exchanger that has two inside spaces, which are partitioned by a partition wall for two heat exchange systems.
The header tank of the heat exchanger of WO 2010/133491A1 includes a core plate (collector plate), a cover and a seal. The core plate has a bottom, which has tube receiving holes and is surrounded by a peripheral groove. The cover has a peripheral lug. The seal is held between the peripheral groove of the core plate and the peripheral lug of the cover and is also held between the core plate and the partition wall of the cover. Furthermore, a portion of the bottom of the core plate, which is opposed to the partition wall, is locally recessed in a view taken from an inside of the header tank, so that the sealing surface of the seal extends in a plane.
In the header tank of WO 2010/133491A1, the sealing surface of the seal extends in the plate, so that a uniform compression force may be achieved along the entire sealing surface of the seal. However, since the portion of the core plate is locally recessed in the view taken from the inside of the header tank, a projecting length of an end portion of the tube, which projects from the recessed portion of the core plate into the inside of the header tank, becomes longer than that of the other tube, which projects from another portion of the core plate that is other than the recessed portion. This construction poses the following disadvantage with respect to the production of the header tank.
Normally, the tubes are fixed to the core plate as follows. That is, each of the tubes is inserted into the corresponding tube receiving hole of the core plate. Then, a dedicated tool is inserted into an opening of an end portion of the tube to widen the opening of the end portion of the tube from the inside of the tube and thereby to plastically deform a connecting portion of the tube, which is connected to the peripheral edge of the receiving hole. In this way, the tube is temporarily fixed to the tube receiving hole. Thereafter, the tube is brazed to the core plate. Therefore, in the case of WO 2010/133491A1, the amount of deformation of the end portion of the tube, which has the long projecting length discussed above, needs to be increased to plastically deform the connecting portion of the tube, which is connected to the receiving hole of the core plate, by a predetermined amount. This might possibly cause cracking of the end portion of the tube. Alternatively, the amount of plastic deformation of the tube at the connecting portion received in the receiving hole might possibly become insufficient. In such a case, a clearance at a brazing part between the tube and the receiving hole might become excessively large to cause a brazing defect. Furthermore, when the tubes are excessively deformed to have an increased width at the end portion of the tube, a size of a space between the end portions of the adjacent two tubes may be reduced. Thereby, a partition plate may be snagged, i.e., caught between the tubes without being held in place at the time of assembling of a tank main body of the header tank, thereby resulting in deterioration of the assembling efficiency. Furthermore, in the header tank of WO 2010/133491A1, the core plate is locally recessed in the view taken from the inside of the header tank, so that a heat exchanging surface area between the tube, which is connected to the locally recessed portion of the core plate, and the air may be reduced at the outside of the header tank in comparison to the other tubes, which are placed at the outside of the locally recessed portion at the core plate.